Fusion splicing device and fusion splicing method

ABSTRACT

It is an object of the invention to provide an apparatus and method for fusion splicing the optical fibers under the fusion splicing conditions suitable for respective optical fibers in which the types of optical fibers can be fully discriminated.  
     The present invention provides a fusion splicing apparatus for fusion splicing the end portions of the optical fibers by butt discharging, comprising an image observing mechanism ( 1 ) for observing the end portions of the optical fibers, an image processing section ( 2 ) for measuring the parameter data of a brightness distribution waveform of optical fiber in cross section from a picked up image, a fuzzy operation section ( 4 ) for obtaining a degree of attribution for the measured parameter data from the fuzzy operation data registered in advance in a data registering section ( 3 ) and identifying the type of optical fiber through a fuzzy operation, a collating section ( 6 ) for collating the identified type of optical fiber with the fusion splicing conditions for each type of optical fiber registered in advance in the fusion splicing condition registering section ( 5 ), a display unit ( 7 ) for displaying the collation result, a fusion splicing mechanism ( 9 ), and a control section ( 8 ).

FIELD OF THE INVENTION

[0001] The present invention relates to an apparatus and method forfusion splicing end portions of optical fibers for communication bydischarge heating and the like, and more particularly to an apparatusand method for fusion splicing the optical fibers under fusion splicingconditions suitable for types of optical fibers by automaticallydetermining the types of optical fibers.

BACKGROUND OF THE INVENTION

[0002] Along with the expansion and diversification of the optical fibercommunications in recent years, various types of optical fibers adaptedfor respective uses have been developed and utilized. Various types ofoptical fibers, including a single mode optical fiber (hereinafterreferred to as an SM fiber), a multi-mode optical fiber (hereinafterreferred to as an MM fiber), a dispersion shifted optical fiber(hereinafter referred to as a DS fiber), and an erbium doped opticalfiber (hereinafter referred to as an ED fiber), are provided. When theseoptical fibers are fusion spliced by a fusion splicing machine, it isrequired to make splicing under the fusion splicing conditions(discharge current, discharge time, etc.) suitable for each opticalfiber. However, the type of the optical fiber may be mistaken, in whichthere is the risk that a splicing failure occurs due to unsuitablefusion splicing conditions for the optical fibers.

[0003] The fusion splicing of the optical fibers is not necessarilyconducted under the light working environment, but may be conductedunder the dark environment within a manhole, for example. In this case,the coating material of the optical fiber may be colored to identify thetype of optical fiber, but recognized by mistake. If image observingmeans of high resolution and high magnification is employed for an imagemonitor of the fusion splicing machine, a core portion as minute as 3 to10 μm can be observed, but the optical fibers of similar profiles may berecognized by mistake.

[0004] If the optical fibers are not spliced under the fusion splicingconditions suitable for the type of optical fiber, a splicing loss isgreater, whereby the splicing of optical fibers must be made again fromthe beginning. To make splicing again, a series of operations, includingthe removal of a falsely spliced portion, the removal of the coatingsfor the end portion of optical fiber and cutting the end portion must beperformed from the beginning, resulting in a worse working efficiency,and the operator becomes nervous.

[0005] One of the conventional techniques to solve the above problem iswell-known in which the optical fibers are spliced under the optimalfusion splicing conditions by identifying the type of optical fiberthrough image processing, as disclosed in JP-A-8-21923. Thisconventional technique involves identifying the brightness level profileof the optical fiber observed at the fusion spliced portion throughimage processing. Then the brightness level profile (hereinafterreferred to as a brightness profile) for each of various types ofoptical fiber is previously stored. Thereafter, the type of opticalfiber is designated by collation with the brightness profile of opticalfiber to be fusion spliced. The optical fibers are fusion spliced bydesignating the type of optical fiber and selecting the optimal fusionsplicing conditions from among the stored fusion splicing conditions foreach type of optical fiber.

[0006] However, when the type of optical fiber is estimated by obtainingthe brightness profile from an observed image of the optical fiber,there are various intricate factors such that the brightness profile maybe varied or different between the same type of optical fibers,depending on the focus or optical characteristics of the observed image,and the manufacturing conditions of the optical fiber. The conventionaltechnique shows an example of a fusion splicing machine for ribbonizedoptical fiber, in which image observing means, typically with a lowmagnification and a long depth of focus, has a small numerical apertureof 0.1 or less. Hence, the resolution can not be sufficiently obtained,whereby it is difficult to acquire the detailed information from thebrightness profile.

[0007] Even if image observing means with high magnification and highresolution is employed for image observation, a DS fiber and an EDfiber, for example, have both a core diameter of 4 μm, with quitesimilar brightness profiles, and practically is difficult todiscriminate from the comparison between the brightness profiles. In theconventional technique, the comparison between the brightness profilesis made employing the interval between displaced points near the centerof fiber axis. Accordingly, although this technique is effective whenthe brightness profile is clearly different depending on the type ofoptical fiber, it is difficult to discriminate all the types of opticalfiber.

[0008] The present invention has been achieved in the light of theabove-mentioned circumstance, and it is an object of the invention toprovide an apparatus and method for fusion splicing the optical fibersunder the fusion splicing conditions suitable for respective opticalfibers in which the types of optical fibers can be fully discriminated.

SUMMARY OF THE INVENTION

[0009] The present invention provides a fusion splicing apparatus forfusion splicing end portions of optical fibers by butt discharging,characterized by comprising an image observing mechanism for observingthe end portions of the optical fibers, an image processing section formeasuring parameter data of a brightness distribution waveform ofoptical fiber in cross section from a picked up image, a fuzzy operationsection for obtaining a degree of attribution for the measured parameterdata from a fuzzy operation data registered in advance in a dataregistering section and identifying the type of optical fiber through afuzzy operation, a collating section for collating the identified typeof optical fiber with fusion splicing conditions for each type ofoptical fiber registered in advance in a fusion splicing conditionregistering section, a display unit for displaying a collation result, afusion splicing mechanism, and a control section.

[0010] Also, this invention provides a fusion splicing method for fusionsplicing end portions of optical fibers by butt discharging,characterized by including observing the end portions of the opticalfibers in an image observing mechanism, measuring parameter data of abrightness distribution waveform of optical fiber in cross section froma picked up image in an image processing section, obtaining a degree ofattribution for the measured parameter data from fuzzy operation dataregistered in advance and identifying the type of optical fiber througha fuzzy operation in a fuzzy operation section, collating the identifiedtype of optical fiber with fusion splicing conditions for each type ofoptical fiber registered in advance in a collating section, displayingthe collation result, and fusion splicing the optical fibers in a fusionsplicing mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a block diagram for explaining an embodiment of thepresent invention.

[0012]FIG. 2 is a view showing a picked up image.

[0013]FIG. 3 is a graph for explaining a brightness distributionwaveform.

[0014]FIG. 4 is a graph for explaining a differential waveform of thebrightness distribution waveform.

[0015]FIG. 5 is a graph for explaining a membership function.

[0016]FIG. 6 is a graph for showing a specific example of the membershipfunction.

[0017]FIG. 7 is a graph for explaining a deviation of the brightnessdistribution waveform.

[0018]FIG. 8 is a view displaying the result of discriminating the typeof optical fiber.

[0019]FIG. 9 is a flowchart showing the embodiment of the invention.

[0020] In these drawings, reference numeral 1 denotes an image observingmechanism, 2 denotes an image processing section, 3 denotes a dataregistering section, 4 denotes a fuzzy operation section, 5 denotes afusion splicing condition registering section, 6 denotes a collatingsection, 7 denotes a monitor display unit, 8 denotes a control section,9 denotes a fusion splicing mechanism, 11 denotes an optical fiber, 12denotes a microscope, 13 denotes a light source, 14 denotes a mirror,and 15 denotes a focus driving section.

BEST MODE FOR CARRYING OUT THE INVENTION

[0021]FIG. 1 is a block diagram for explaining an embodiment of thepresent invention. In FIG. 1, reference numeral 1 denotes an imageobserving mechanism, 2 denotes an image processing section, 3 denotes adata registering section, 4 denotes a fuzzy operation section, 5 denotesa fusion splicing condition registering section, 6 denotes a collatingsection, 7 denotes a monitor display unit, 8 denotes a control section,9 denotes a fusion splicing mechanism, 11 denotes an optical fiber, 12denotes a microscope, 13 denotes a light source, 14 denotes a mirror,and 15 denotes a focus driving section.

[0022] The image observing mechanism 1 picks up an image of a pair ofoptical fibers 11 butted and held by the fusion splicing mechanism (notdescribed in detail and not shown) from two directions using themicroscopes 12 with the CCD cameras disposed orthogonal to each other.The light source 13 for illumination to pick up the image is disposed toilluminate the optical fiber 11 via the mirror 14 from the backgroundside. The microscope 12 of high magnification and high resolution hasthe focus driving section 15 for adjusting the focal point, which iscontrolled by the control section 8 with a microprocessor.

[0023] An optical fiber image observed by the microscope 12 is measuredto acquire the predetermined data of optical fiber from the brightnessdistribution waveform in the image processing section 2. For themeasured data, a degree of attribution is calculated by referring to thedata of a fuzzy data memory registered in advance in the dataregistering section 3 in the fuzzy operation section 4. The degree ofattribution for each of a plurality of types of optical fiber iscompared and calculated to select a candidate for the type of opticalfiber, verify the validity of the candidate and decide the type ofoptical fiber.

[0024] If the type of optical fiber is decided, the collating section 6collates the type of optical fiber and the fusion splicing conditions ofthat type registered in advance in the fusion splicing conditionregistering section 5. If the fusion splicing conditions are matchedwith the set conditions, the optical fibers are spliced under the setfusion splicing conditions using the fusion splicing mechanism 9. If thefusion splicing conditions are unmatched with the set conditions, aninstruction for retry or splicing is made. The collation result of thecollating section 6 is displayed on the monitor display unit 7. Theexecution of fusion splicing is made under the registered fusionsplicing conditions by controlling the fusion splicing mechanism 9 inthe control section 8 with the microprocessor. The details of eachsection will be described below.

[0025] First of all, the image processing section 2 comprises imageacquisition means 2 a for acquiring the optical fiber image picked up bythe image observing mechanism 1, waveform detecting means 2 b fordetecting the image as a brightness distribution waveform (hereinafterreferred to as a brightness profile), and data measuring means 2 c formeasuring the data from the brightness profile.

[0026]FIG. 2 is a view showing an image pick-up screen of the opticalfibers to be acquired by the image acquisition means 2 a. In FIG. 2, theends of a pair of optical fibers to be fusion spliced are butted beforebeing fusion spliced. Light passing through the optical fiber iscondensed because the optical fiber serves as a rod lens, and has abrightness distribution where light is centrally condensed. Therefore,the transmitting light is condensed in the dark portion as a shadowagainst the background light brightness.

[0027] On the image pick-up screen, a strip image is displayed,consisting of a bright portion 21 of the transmitting light appearinghorizontally in the central section and a dark portion 22 as a shadowappearing on both the upper and lower sides of the bright portion 21. Abrighter portion 23 appears in the center of the bright portion due to acore portion having a different refractive index. This picked up imageis extracted along a sampling line 24 and arithmetically operated toobtain the brightness profile. The sampling is made at several points(four to five points), whereby the average value data is obtained.

[0028]FIG. 3 is a graph showing the brightness profile of the opticalfiber in cross section for the image of FIG. 2, in which the brightnessof the optical fiber is indicated along the longitudinal axis and theposition in diameter direction is indicated along the transverse axis.This brightness profile consists of a bright portion 25 in the centralsection, a dark portion 26 on both sides thereof, and a bright portionindicating the background brightness in its outside. The bright portion25 in the central section has a projecting crest 27 in the center, andcrests 28 on the left and right sides thereof. The number of crests, itsinterval and the height of crest may be different depending on the typeof optical fiber. The central crest 27 indicates the core portion, andis relatively easily identified to be located almost in the center ofthe optical fiber. A trough 30 is also easily recognized on both sidesof the central crest 27.

[0029] Differentiating the brightness profile of FIG. 3, a differentialvalue waveform is obtained as shown in FIG. 4. The position and numberwhere the differential value is equal to zero are different depending onthe number of crests, but a vertex position 29 of the crest 27 for thecore portion is easy to obtain. The distance between the maximumdifferential values across the vertex position 29 as the center wherethe differential value is zero is defined as a core diameter A, and thedistance between the differential values of zero on both sides of thevertex position 29 is defined as a core diameter B. As shown in FIG. 3,the core diameter A indicates a variable density boundary distance(width) at the middle abdomen of the crest 27 in the core portion, andthe core diameter B indicates a distance between the troughs 30. Also,the number of crests is equal to the number of peaks in the angularwaveform, and a brightness difference (or a core height) between thevertex position 29 of the crest 27 and the trough 30 in the core portionis measured and acquired as the data. Besides, the height of crest 27may be represented by the brightness level from the dark portion 26, butnot from the trough 30, or the contrast may be obtained as the data.

[0030] Usually, the SM fiber has a waveform of three crests as shown inFIG. 3, in which a central crest indicates the core portion. Each of theDS fiber and the ED fiber has actually a small core diameter and a largedifference in refractive index between the core and the cladding,whereby the central crest 27 for the core portion is slender and higher.Further, since the refractive index distribution is convex, the lightcondensing is so complex that the bottom of the crest is spread or thenumber of crests is increased. On the other hand, the MM fiber (GI type)has a refractive index that gradually changes, with the height of cresttending to decrease conspicuously.

[0031] In this manner, the brightness profile of optical fiber isdifferent depending on the type of optical fiber, and measured by thedata measuring means 2 c. The degree of attribution is substituted forthe data measured from the brightness profile by the fuzzy operationsection 4. The type of optical fiber is identified from the degree ofattribution obtained. In making a fuzzy operating process, it isrequired to prepare for the membership function. Turning back to FIG. 1,the data registering section 3 will be described below.

[0032] The data registering section 3 stores in advance the data fordiscriminating the types of optical fibers to be fusion spliced. Thedata registering section 3 includes data processing means 3 a and afuzzy data memory 3 b. The data processing means 3 a creates themembership function data by calculating an average value and a standarddeviation value from the data measured by the image processing section.Also, it acquires the newly measured data as the additional data andupdates the data. The fuzzy data memory 3 b accumulates the opticalfiber type data subjected to the fuzzy operation by the data processingmeans and is used for calculating the degree of attribution for theoptical fiber that is newly measured.

[0033]FIG. 5 is a typical example of the membership function useful inthe fuzzy operation of the invention, in which the membership functionis a convex type. This function represents the fuzziness of data in thedistribution width, and has a probability that the degree of attributionis one at the central value. However, other forms or the general fuzzytheory may be employed, so long as the distribution of data isrepresented by the function. The membership function of FIG. 5 isrepresented by a triangle with a vertex at the central value and thedistribution width as the bottom side, in which the degree ofattribution is taken along the longitudinal axis, and the parameter dataalong the transverse axis. The central value is an average value of dataand the distribution width is a standard deviation value. By making thedistribution width several times (e.g., five times on one side) thestandard deviation value, the membership function is so reasonable thatmeasurement values are not deviated from the average value and do notbecome zero over the broad range.

[0034]FIG. 6 shows the examples of the membership function from theactual measurement data. FIG. 6(A) is a membership function with thecore diameter A, FIG. 6(B) is a membership function with the corediameter B, FIG. 6(C) is a membership function with the core height, andFIG. 6(D) is a membership function with the number of crests. As will beseen from these figures, in the core diameter B (distance between thetroughs 30 in FIG. 2), there is no vivid difference between the SM fiberand the MM fiber, and there is also no apparent difference between theDS fiber (DS1 indicates an ordinary dispersion shifted optical fiber andDS2 indicates a dispersion shifted optical fiber of core expansion type)and the ED fiber, when the standard deviation is included. In creatingthe membership function, the application range may be misjudged to benarrow.

[0035]FIG. 7 is a graph showing the variation of the brightness profilewhen the focus positions (three positions) of the SM fiber are changed.As shown in FIG. 5, the brightness profile is varied by changing thefocus position for picking up the image even with the exactly sameoptical fiber. Accordingly, it is necessary to extend the distributionwidth of the membership function by intentionally dispersing theprofile, including the values measured at the positions before and afterthe focus set-up position, to increase the adaptability.

[0036] The membership function is necessary to be created in advancefrom the known data or by the data registration. However, when thefusion splicing is made by newly discriminating the type of opticalfiber, it is possible that the measured data for discrimination is newlyadded to the already existing membership function. Also, the types ofoptical fiber can be further distinguished by adding the new fiber asdefined by the user successively and learning it. By the successiveaddition of data, the amount of database for discrimination can beincreased, and the type of optical fiber can be identified more minutelyand precisely.

[0037] The additional data can be managed in accordance with thefollowing expression,

AV _(n+1)=(n·AV _(n) +D _(n+1))/(n+1)  (1)

σ_(n+1) ²=[(n−1)·σ_(n) ² +n·AV _(n) ² +D _(n+1) ²−(n+1)·AV _(n+1) ²]/n  (2)

[0038] where n is the number of data, AV_(n) is an average value, σ_(n)is a standard deviation value, and D_(n+1) is the addition data.

[0039] Herein, if the number n, the average value and the standarddeviation value are already known, the optimization can be performed dueto the addition of data. Since the weight in adding the data is changedby changing the number n, the extent of adaptability or the learningspeed (number of additions) can be set up.

[0040] Turning back to FIG. 1, the fuzzy operation section 4 fordiscriminating the type of optical fiber will be described below. Thefuzzy operation section 4 includes fuzzy operating means 4 a, comparingcalculating means 4 b, candidate verifying means 4 c and fiber typedeciding means 4 d. The fuzzy operating means 4 a substitutes the degreeof attribution for the data measured by the image processing section 2.The substitution of the degree of attribution is made for the measureddata as the type of optical fiber from the membership function of FIG. 6stored in the fuzzy data memory 3 b.

[0041] Table 1 lists an instance of calculating the degree ofattribution. The numerical values of Table 1 are only exemplary forexplanation, but differ from the actual values. TABLE 1 Number of Corecrests diameter B Core height Type (3) (9 μm) (60) Minimum SM 0.8 0.50.8 0.5 MM 0.9 0.8 0.3 0.3 DSl 0.9 0.8 0.9 0.8 ED 0.5 0 0.8 0 Maximum0.8

[0042] The calculation of Table 1 will be described below. Assuming thatthe number of measured crests for the bright portion is three, it willbe found from the membership function of FIG. 6D that the SM fiber, theMM fiber, the DS1 fiber and the ED fiber have the degrees of attributionof 0.8, 0.9, 0.9 and 0.5, respectively. Similarly, assuming that thecore diameter B is 9 μm, and the core height is 60 steps, those opticalfibers have the degrees of attribution for the type of optical fiber aslisted in Table 1, which are calculated from the membership function foreach parameter of FIG. 6.

[0043] The numerical values calculated by the fuzzy operating means 4 aare employed by the comparing calculating means 4 b to select acandidate for the type of optical fiber of measured data. The candidateselection is made using a minimum/maximum method. This minimum/maximummethod involves firstly selecting the minimum degree of attribution foreach type of optical fiber. In Table 1, the SM fiber is 0.5 for the corediameter B, the MM fiber is 0.3 for the core height, the DS1 fiber is0.8 for the core diameter B, and the ED fiber is zero for the corediameter B. Then, the maximum degree of attribution is selected fromamong the minimum degrees of attribution for each type of optical fiber.That is, since the maximum degree of attribution is 0.8 for the DS1fiber, it is judged that the candidate for the type of optical fiber isthe DS1 fiber.

[0044] An arithmetical expression for the minimum/maximum method isrepresented in the following manner. Herein, F is a degree of confidencehaving a numerical value of the degree of attribution, m is a membershipfunction, “i, j, k, l, . . .” are parameters, and t is the type ofoptical fiber.

[0045] F=max[min(m_(i), t, m_(j), t, m_(k), t, m_(l), t, . . . )]t

[0046] The type of optical fiber as determined in the above manner isverified by the candidate verifying means 4 c. The verification of thecandidate is uncertain, when the degree of attribution for the type ofoptical fiber determined as the candidate is small, because the degreeof attribution selected for the candidate is the degree of confidence.Accordingly, if a threshold is set for the degree of attribution, theidentification of the candidate may be unclear when the candidate hasthe degree of attribution smaller than this threshold. In selecting thecandidate with the maximum degree of attribution, two candidates havingthe same maximum degree of attribution or with a smaller difference inthe degree of attribution between the first and second candidates than acertain value, if any, are displayed. In this case, the type of opticalfiber may be decided by making the measurement again, or on the basis ofthe ranking.

[0047] As a result that the type of optical fiber is verified by thecandidate verifying means 4 c, if the verification is good, thecandidate is decided by the fiber type deciding means 4 d. A Table 2below lists the results of sampling test, which are almost satisfactory.The precision of identification can be further raised by addition andaccumulation of data, as previously described. TABLE 2 Fiber Type Numberof Correct Correct Answer Ratio SM 36/36 100% MM 35/36 97% DS1 34/36 94%(Normal type) DS2 36/36 100% (Expanded core area type) ED 35/36 97%

[0048] The result of determining the type of optical fiber is displayed,along with the fiber image, on the monitor display unit 7, as shown inFIG. 8. The determination for the type of optical fiber is madeseparately for each of the left and right optical fibers. The type ofoptical fiber is displayed for each of the left and right opticalfibers, in which the splicing conditions may be displayed. The operatormay be prompted to perform the fusion splicing or retry by onceinterrupting the operation during this display. In deciding the type ofoptical fiber, the type of optical fiber and the measurement data areadded to the data registering section 3.

[0049] If the type of optical fiber is decided, the type of opticalfiber is collated by the fusion splicing condition registering section 5and the collating section 6. The fusion splicing condition registeringsection 5 includes setting means 5 a for inputting the splicingconditions and a memory 5 b for storing the splicing conditions. Thesplicing conditions include the preheating time, end face spacing,discharge current, and discharge time for each type of optical fiber,for example.

[0050] After the type of optical fiber and the fusion splicingconditions are collated by the collating section 6, the fusion splicingis performed automatically or by confirmation of the operator. If thecollation results are matched with the type of optical fiber and thefusion splicing conditions selected beforehand by the operator prior tosplicing, the fusion splicing is automatically performed withoutinterruption. In this case, the results are not displayed on the monitordisplay unit 7, thereby lightening the labor of the operator. Only ifthe collation results are unmatched with the type of optical fiber andthe fusion splicing conditions, the results are displayed on the monitordisplay unit 7 to prompt the operator to perform the fusion splicing orretry in accordance with the display contents. The fusion splicingitself is performed by driving the fusion splicing mechanism 9 (notshown in detail) on the basis of the above-mentioned fusion splicingcondition under the control of the control section 8 withmicroprocessor, employing the well-known method and mechanism.

[0051] Referring to a flowchart of FIG. 9, a fusion splicing method ofthe invention will be described below. In FIG. 9, the automaticprocessing is shown within the frame of the dotted line, and the manualprocessing is shown outside the frame. A flow of fiber registration tocreate the fiber data for determining the type of optical fiber is shownon the left side of the flowchart, and a flow of fusion splicing isshown on the right side.

[0052] First of all, the flowchart of the fiber registration on the leftside will be described below. Herein, a pair of optical fibers withclear type of optical fiber are set in the fusion splicing apparatus, asis the case of fusion splicing. Firstly, the optical fibers are set.Then, at step S1, the type of optical fiber (one of the choices ifalready known or its name if unknown) is selected and input. The nextsteps D2 to D5 involve the image processing of optical fiber.

[0053] At step D2, light adjustment is made by the image observingmechanism (FIG. 1) so that an observed picked-up image of the opticalfiber may be in an optimal state. Then, at step D3, the butt position isadjusted so that the pick up position of the optical fiber may belocated in the center of the screen to be easily observed. Thereafter,at step D4, focusing is made to set the focal point of observed image ata preset focus position.

[0054] At step D5, the data of the optical fiber is measured. The datameasurement is made by sampling several points on a butt screen (FIG. 2)of the optical fiber and creating the brightness profile (FIG. 3) of theoptical fiber through the image processing. A differentiating processing(FIG. 4) is performed on the basis of this brightness profile to acquirethe parameter data, including the core diameter, core height and thenumber of crests.

[0055] At step D6, the measured data is processed. The data processinginvolves creating the membership function (FIGS. 5 and 6) on the basisof the measured data, in which the created data is registered as thefiber data in the database. Thereafter, at step D7, the optical fiber isremoved from the fusion splicing apparatus.

[0056] A flow of the fusion splicing on the right side will be describedbelow. Herein, the type of optical fiber may be already known butuncertain, or unknown absolutely. A pair of optical fibers to be fusionspliced are set in the fusion splicing apparatus as is the case with thefiber registration. After the optical fibers are set, at step S1firstly, the fusion splicing conditions are selected and input. Thefusion splicing conditions that are relevant with the type of opticalfiber maybe selected by the type of optical fiber. The fusion splicingconditions are selected from among the pieces of splicing condition dataregistered in the database on the basis of the presumption of the typeof optical fiber, if it is estimated in advance. If the type of opticalfiber is unknown absolutely, an item “automatic selection” provided onthe selection menu may be chosen.

[0057] The light adjustment at step S2, the butting at step S3, thefocusing at step S4, and the fiber measurement at step S5 are involvedin the image processing as previously described, with the exactly sameflow as the fiber registration, and not described here. The datameasured in the fiber measurement at step S5 may be added to thedatabase, as needed, or the processing of fiber registration at step D6may be performed in parallel.

[0058] The steps S6 to S8 are involved in the determination of the typeof optical fiber and the splicing collation of the fusion splicingconditions. At step S6, the type of optical fiber that has been set isidentified. Identification of the type of optical fiber is made bycalculating the degree of attribution for the data measured at step S5by referring to the fuzzy operated data (FIG. 6) in the database, andidentifying the type of optical fiber by the minimum maximum method.

[0059] After the fiber type is identified at step S6, the fusionsplicing conditions for each type of optical fiber registered in thedatabase are collated. If they are matched with the fusion splicingconditions selected at step S1, the operation proceeds to the nextfusion splicing processing. If unmatched with the fusion splicingconditions selected at step S1, the collation result is displayed on thedisplay unit at step S8. If the splicing is determined to be unsuitablefrom the displayed data, the operation returns to step S1 to set thefusion splicing conditions again. If it is determined that the splicingis possible though the displayed data is unmatched, the operationproceeds to the next fusion splicing processing.

[0060] The next steps S9 to S13 involve performing the fusion splicingof the optical fibers by the well-known method. First of all, inmeasuring the end face of optical fiber at step S9, the end face spacingbetween optical fibers, the end face shape of the optical fiber, andattachment of dust are measured. At step S10, if the end face shape ischecked to be false, the optical fiber is removed from the apparatus,and cut again. If there is no abnormality on the end face of opticalfiber, the optical fibers are aligned with their axes at step S11.Subsequently, at step S12, the optical fibers are fusion spliced at adischarge current and for a discharge time set in the fusion splicingconditions. And in the check after fusion splicing at step S12,appearance of the spliced portion for thickness or thinness, the mixtureof dust and air bubbles, the inclination of core portion, andmisalignment are checked. Thereafter, at step S14, the optical fiber isremoved from the fusion splicing apparatus.

[0061] A single core optical fiber has been described above, but theinvention is also applicable to a ribbonized optical fiber, employingthe image observing mechanism with high magnification. In this case, ifthe ribbonized optical fiber is apparently composed of optical fibers ofthe same kind, one of the ribbonized optical fibers may be subjected tothe identification processing.

[0062] Though this invention has been described above in connection withthe specific embodiments, it will be apparent to those skilled in theart that various variations or modifications may be made thereto withoutdeparting from the scope or spirit of the invention.

[0063] This application is based on JP-A-2000-369681, dated on Dec., 5,2000, its contents being incorporated herein by reference.

INDUSTRIAL APPLICABILITY

[0064] As will be apparent from the above description, with thisinvention, the optical fibers can be suitably fusion spliced byidentifying all the types of optical fibers correctly and selecting thefusion splicing conditions suitable for the type of optical fiber. Also,it is possible to add to the database for identification automatically,and increase the identification precision.

What is claimed is:
 1. A fusion splicing apparatus for fusion splicingend portions of optical fibers by butt discharging, characterized bycomprising: an image observing mechanism for observing the end portionsof the optical fibers; an image processing section for measuring aparameter data of a brightness distribution waveform of optical fiber incross section from a picked up image; a fuzzy operation section forobtaining a degree of attribution for the measured parameter data from afuzzy operation data registered in advance in a data registering sectionand identifying the type of optical fiber through a fuzzy operation; acollating section for collating the identified type of optical fiberwith fusion splicing conditions for each type of optical fiberregistered in advance in a fusion splicing condition registeringsection; a display unit for displaying the collation result; a fusionsplicing mechanism; and a control section.
 2. The fusion splicingapparatus according to claim 1, characterized in that said parameterdata includes at least the number of crests, a core diameter, and a coreheight of said brightness distribution waveform.
 3. The fusion splicingapparatus according to claim 2, characterized in that said dataregistering section comprises data processing means for retrieving saidparameter data and creating the fuzzy operation data.
 4. The fusionsplicing apparatus according to any one of claims 1 to 3, characterizedin that the fuzzy operation data registered in advance is a membershipfunction of an average value and a standard deviation value for theparameter data of the brightness distribution waveform of the opticalfiber in cross section.
 5. A fusion splicing method for fusion splicingend portions of optical fibers by butt discharging, characterized byincluding: observing the end portions of said optical fibers in an imageobserving mechanism; measuring a parameter data of a brightnessdistribution waveform of optical fiber in cross section from a picked upimage in an image processing section; obtaining a degree of attributionfor the measured parameter data from a fuzzy operation data registeredin advance and identifying the type of optical fiber through a fuzzyoperation in a fuzzy operation section; collating the identified type ofoptical fiber with fusion splicing conditions for each type of opticalfiber registered in advance in a collating section; displaying thecollation result; and fusion splicing the optical fibers in a fusionsplicing mechanism.
 6. The fusion splicing method according to claim 5,characterized in that said parameter data includes at least the numberof crests, a core diameter, and a core height of said brightnessdistribution waveform.
 7. The fusion splicing method according to claim5 or 6, characterized in that the fuzzy operation data registered inadvance is a membership function of an average value and a standarddeviation value for the parameter data of the brightness distributionwaveform of the optical fiber in cross section.
 8. The fusion splicingmethod according to claim 7, characterized in that said membershipfunction involves the parameter data where said brightness distributionwaveform has a focal point for picking up an optical fiber image shiftedfrom a set-up position.
 9. The fusion splicing method according to claim7 or 8, characterized in that said membership function has additionallysaid measured parameter data of the optical fiber to be fusion splicednewly.
 10. The fusion splicing method according to any one of claims 5to 7, characterized by further including obtaining degree of attributionfor each of plural pieces of said measured parameter data for each ofplural types of optical fiber to make the fuzzy operation, selecting theminimum value of said degrees of attribution for each type of opticalfiber, selecting the maximum value among said selected minimum values,and identifying the type of optical fiber indicating said selectedmaximum value as the type of measured optical fiber.
 11. The fusionsplicing method according to claim 5, characterized in that if thecollation result of the splicing conditions for the identified type ofoptical fiber is matched with the preset splicing conditions, the fusionsplicing is performed without displaying the collation result.